import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
     private DatagramSocket socket = null ;

    public UdpEchoServer(int port) throws SocketException {
        this.socket = new DatagramSocket(port);
    }
    public void start() throws IOException {
        System.out.println("启动服务器");
      while(true){
          DatagramPacket requestPacket = new DatagramPacket(new byte[4096], 4096 );
           socket.receive(requestPacket);
           String request = new String (requestPacket.getData() , 0, requestPacket.getLength()) ;

           String response = process(request) ;
           DatagramPacket responsePacket = new DatagramPacket(response.getBytes() , response.getBytes().length
            , requestPacket.getSocketAddress()) ;
           socket.send(responsePacket);
          System.out.printf("[%s ,%d]request=%s , response = %s\n" ,requestPacket.getAddress().toString() ,
                  requestPacket.getPort() ,request , response);
      }
    }

    private String process(String request) {
        return request ;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer udpEchoServer = new UdpEchoServer(6060) ;
        udpEchoServer.start();
    }
}
